I have a 1991 Camaro RS with the 3.1L engine. I have changed the thermostat, radiator cap, and flushed out the system with a Flush from Prestone. The car stays around 195 as long as you are running down the road. When you slow down in stop and go traffic or just sit it will heat up but as soon as you are driving it won't heat up. It goes to around 230 and when you turn off the car it immediately starts to boil over. What should I replace next. Water Pump, Fan, Radiator. The fan already stays on all the time.

 

you mean your coolant will actually start to boil???
if so, first i would check to see if your fan is working (power, fuses), then i would think that maybe your radiator has become clogged, you may want to take it somewhere and have that looked at. my 3.1 seemed to constantly run at about 220 and sometimes heated up the way you described but never had it boil over (my friends did by the way, but i cant remember how we fixed it), i decided that because these cars are pretty notorious for running hot that i would run a dryer hose from the airbox down the inside of the passenger quarter panel and point it towards the front of the car. that way the engine was no longer recycling all that hot air and had a chance to get some fresh air. you may give that a try
jesus..i hope that made sense
-pat

 

I am hoping you do NOT mean the fan stays on from the moment you turn the key/engine starts.
Then you have a fan sensor problem or a computer problem.
My fan stayed on all the time. replaced computer & fixed that.

It could be radiator clogged.
You cannot see into the radiator.
Check the condition of the hoses.
The fan shuts off when ya shut off the car.
It should turn on at 220* or less.
Water pump is bad when it's bad (it'll leak!).
Sounds like maybe too much water, also. Let it "burp" itself and see what happens (fluid level stays the same, ovenight). Then check in AM to see how much in radiator/not overflow bottle.
Look for any restictions in front of the radiator.

------------------
Chat Soon,
KED85
Karl
1985 Firebird 2.8 to 3.4 swap project for Smog Happy LA, CA

 

What I mean by the fan stays on all the time is that as soon as you turn the key on the fan comes on and when you turn off the key the fan goes off. I would think this would be a plus because it is always blowing air on the radiator. I know that I need to fix the sensor but in the meantime I just want it to quit heating up.